Why the L/D is same to the glide ratio?

3 Answers

Let’s think about this for a minute. The L/D curve shows you how airspeed will affect both lift and drag. You want to find an airspeed that has minimal drag and maximum lift. This speed is called L/Dmax.

When you glide, you are converting potential energy (altitude) to kinetic energy (airspeed). You would want to find an airspeed that gives the most efficient transfer of energy. You want to find an airspeed that will allow the airplane to stay in the air the longest amount of time. This sounds to me like you want to have maximum lift and minimum drag. The same as L/Dmax.

“When straight and level, V=75kts L/D=12. If engine die. V is still 75kts, and we have 25kts head wind. What is the glide ratio?”

You’re issues a point of reference question. Relative to the ground you’re glide ratio got worse, or would be 8 if my mental math is right. Relative to air passing over the wing it remains the same.

However, glide ratio is given in a no wind condition. It’s up to the pilot to take the wind conditions into account when calculating a glide distance.

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